Triglycerides obtained from natural sources consist of numerous different fatty acids which may vary in the number of carbons, substitution pattern, degree of unsaturation as well as stereo chemistry. In fish oil for example, over 50 different fatty acids have been found including the commercially important and biological active omega-3 fatty acids: eicosapentaenoic acid (EPA), decosahexaenoic acid (DHA) and docosapentanoic acid (DPA). Omega-3 fatty acids have been associated with beneficial health effects for humans and animals, especially in the area of cardiovascular disease, inflammation and cognitive function and development [1-3]. Therefore, there is a desire to purify the omega-3 fatty acids from sources such as fish oil, algae oil and seal oil.
In vegetable oil, a number of different fatty acid can be found as well, such as trans-11 oleic acid (vaccenic acid) and cis-6,9,12 octadecatrienoic acid (gamma-linolenic acid (GLA)). Dehydrated hydrogenated castor oil is a good source for vaccenic acid, whereas borage oil and evening primrose oil are good sources for GLA. GLA is a fatty acid that has been linked to positive health effects as well, such as the modulation of the immune system, treatment of atopic eczema, rheumatoid arthritis, diabetic neuropathy and cirrhosis of the liver [4]. Milk fat represents another source of bioactive fatty acids like trans-vaccenic acid and conjugated fatty acids.
Due to the strong positive biological effects of several fatty acids, fatty acids can be used as food supplements, as food/feed ingredients as well as pharmaceuticals. However, the concentration of e.g. omega-3 fatty acids in natural sources are low, therefore there is a need for a process that can increase the concentration of the desired fatty acids. Previously, short path distillation, low temperature solvent crystallization, solvent winterization and urea complexation have been utilized.
These methods are expensive and time consuming thereby contributing to the high processing costs of the concentrated fatty acids. Recently, enzymatic reactions (hydrolysis, esterification etc.) have been contemplated and explored as ways of enriching DHA/EPA as free fatty acids [5], ethyl esters [6] or as hexyl esters [7]. In addition, the technology has been used to enrich GLA as a free fatty acids [8] and isomers of conjugated linoleic acid (CLA) [9] as alkyl esters. The limitation of those methods are either the low yield of the final product, or the number of processing steps, both having a direct impact on the cost of the product.
Accordingly, what is needed is a process that is simpler, consisting of fewer processing steps, resulting in a product of higher purity in a higher yield. Large volumes of EPA/DHA are supplied to the world marked as ethyl esters. Therefore, enriching EPA/DHA as ethyl esters would save processing steps and thereby time and costs.